Fission and fusion are two types of nuclear reactions. Fission involves splitting heavy nuclei like U-235, releasing energy. It can be uncontrolled, as in atomic bombs, or controlled in nuclear power plants using moderators and control rods. Fusion combines light nuclei like hydrogen into heavier elements like helium and releases even more energy, but requires extremely high temperatures found in stars like the sun or experimental facilities on Earth.

1. 28.3 Fission and Fusion

3. Figure 19.4: Unstable nucleus.

5. Representation of a fission process.

8. Diagram of a nuclear power plant.

9. Schematic of the reactor core.